The Reds have lost their last two games at home to Southampton and away to Manchester United 1-0 after conceding from a corner both times.
"To concede two goals like that in the past two games was bitterly disappointing and it cost us," Rodgers told the Liverpool Echo.
"We have been let down by us not doing our job in what is arguably the easiest part of the game. It's not tactical or physical, it's all about concentration – that is the biggest thing.
"That is one area of the game we have to be better at. It's something we will address and improve upon."
The Reds travel to the Stadium of Light to face rock-bottom Sunderland today.